Microscope stages are generally required to be highly accurate and repeatable along all motion axes. Typically, a microscope stage will have three orthogonal axes: X, Y, and Z, which are generally defined by the optical axis of the microscope. For most applications, motion along the Z axis should be characterized by high resolution, for example step distances of less than about 0.10 μm, and high repeatability, for example error between multiple visits to the same targeted Z location of less than about 0.20 μm. Additionally, microscopy systems generally attempt to minimize cross-coupling between motion in the Z and X and Y coordinate axes, since such cross-coupling tends to distort the data captured during imaging operations, which in turn decreases quality and usability of the data acquired. A typical Z scan of a microscope slide may consist of 65 points taken on 0.20 μm intervals, for a total Z axis displacement of 13 μm. Ideally, cross-coupling movement in the X or Y axes in such applications would be limited to about 0.40 μm or less throughout the total 13 μm Z scan.
In accordance with conventional stage technologies, as exemplified in the assignee's U.S. Pat. Nos. 6,781,753 and 5,812,310, the disclosures of which are hereby incorporated by reference in their entirety, a conventional microscopy system stage utilizes a series of linear slides in a ramp configuration. The slides and ramp cooperate to guide a microscope slide, disposed on the stage, in the Z dimension. Such multiple linear slide configurations required to create a Z translation, by necessity, are over-constrained. Consequently, parts tolerance, specifications, and assembly methods must be extremely accurate, otherwise the slides will “fight” each other during motion. This can cause binding along the Z axis, which results in high repeatability errors.
Additionally, conventional systems are typically associated with attendant high costs, which result from the foregoing specification, tolerance, and assembly requirements. For example, six separate linear slides and multiple custom machined plates or slide mounts may be required in order to enable Z axis translation in a conventional system.